On Thu, Apr 7, 2011 at 15:49, Ryan Yan <vyan2000 at gmail.com> wrote:
> I agree that solves are faster than factorization and GMRES > use more MatVecMult, even with exact preconditioner. So I guess > PREONLY is meaning direct solve without forming any sub-space and just > one forward and backward substitutions? > Yes. Because of the way GMRES works with zero initial guess, there will be two MatSolve and one MatMult even when using a direct solver. PREONLY does one MatSolve and zero MatMult. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110407/dae5ec5f/attachment.htm>
